1. Technical Field
The present invention relates generally to an apparatus and method for controlling stabilization of a satellite-tracking antenna. More particularly, the present invention relates to an apparatus and method for controlling stabilization of a satellite-tracking antenna, the apparatus and method being capable of avoiding a keyhole problem, which occurs due to reduction in a degree of freedom of an antenna driving axis, by considering an azimuth and driving torque of an elevation motor, and of ensuring communication quality.
2. Description of the Related Art
Satellite communication is performed by transmitting and receiving radio signals to and from an artificial satellite. In satellite communication, installation of a base station is unnecessary, and the desired sight of communication is easily realized. Thus, importance and utilization thereof have increased rapidly in military operations as well as in civilian use. Also, for satellite communication, all platforms including stationary as well as mobile ground vehicles, trains, ships, aircrafts, etc. require communication equipment mounted thereon to track the satellite stably regardless of movement of the platforms.
An artificial satellite is far from the ground, and thus an antenna having narrow beam width and high directivity is used to track the artificial satellite for communication. For example, in the case of a biaxial antenna, an elevation of zero degrees is defined as a direction perpendicular to an azimuth motor axis. In order for the antenna to track the satellite, when a platform moves or disturbance occurs, or the artificial satellite moves, driving torque of an azimuth motor increases in proportion to 1/cos (elevation). Therefore, when the elevation is close to 90 degrees, it is difficult for the antenna to precisely face the artificial satellite. When the elevation is 90 degrees, it is impossible for the antenna to face the artificial satellite. This phenomenon is called keyhole.
That is, a conventional antenna having a biaxial pedestal structure cannot avoid keyhole problem where the elevation is 90 degrees. In contrast, when the elevation is increased equal to or greater than a particular value in order to avoid the keyhole problem, driving of the antenna may be stopped but a tracking error may increase, whereby communication quality may not be ensured.
Also, the keyhole problem occurs due to reduction in one rotational degree of freedom. The keyhole problem may be solved by increasing the number of driving motors, but the height and the volume of the antenna increase as well as power consumption and the weight. Thus, the center of gravity is high such that the stability of the platform is reduced.